1. Technical Field
This disclosure generally relates to air pressure relief valves and more particularly, to pressure relief valves and methods of regulating conditions within an interior compartment utilizing active material actuation.
2. Background Art
It is appreciated that pressure differentials between interior spaces or compartments and the external environment can cause undesirable conditions. For example, in an automotive setting, it can cause an increase in “boom” (i.e., low level noise discomfort), required door closure force, and especially when sudden, discomfort to the occupants of the space. As such, pressure relief valves (PRV's) for reducing pressure differential, which may increase upon the closure of a swing panel (e.g., door, lift flap, rear hatch, etc.) or window, activation of the HVAC system or air bag deployment, opening of a window during movement of the vehicle, so as to cause a Bernoulli effect. These valves are generally located within an interior panel that interfaces with the compartment and the environment (e.g., the structural panel between the rear seat and trunk compartment, the structural panel between the floor and the external environment, the structural panel between the dashboard and the engine compartment, and the like). Structurally, conventional PRV's include at least one conduit fluidly coupling the interior space and exterior environment, and a movable flap (e.g., gate) disposed over an opening defined by the conduit. The flap is passively manipulated in response to the pressure differential. For example, when air pressure within the interior compartment is greater than the external air pressure, the flap opens to compensate for as well as alleviate the increased pressure; and, when the interior compartment air pressure is less than the external air pressure the movable flap covers the opening to prevent air from entering the interior compartment.
More recently, active PRV's, which utilize a drive mechanism to open and/or close the flap, have been developed to address some of the limitations of passive PRV's. In these configurations, pressure differential is no longer required to actuate the PRV; instead, through sensory or manual input, it is appreciated that active PRV's can be triggered by and used to address other conditions, such as poor air quality either interior or exterior to the compartment, excessive temperature, a detect by a sensor, and the operation or status of an associated system. Active PRV's, however, also present various concerns in the art. For example, prior art active PRV's, including those that utilize motors, solenoids, and active material actuation (such as presented by co-owned U.S. Pat. No. 7,204,472 A) to effect the motion of the flap, typically require constant power to maintain the valve in the manipulated condition. This invariably results in a drain upon the power supply. Moreover, with respect to prior art active material based PRV's, the lack of load limit protection resulting in an inability to avoid failure and the costs associated therewith is also of concern. For example, it is appreciated that where the opening of the flap is blocked by a foreign object, the active material element in these PRV's may overheat, become damaged, or otherwise fail.